According to the general prior art the structuring of foodstuffs can be accomplished in various ways. Two main routes can be distinguished:
(1) the structuring by biopolymers such as proteins and carbohydrates, and PA1 (2) the structuring by "particles" in the widest sense.
In the former case polymeric molecules cross-link to form a tangled, interconnected molecular network in water. In those systems the presence of junction zones or entanglements leads to gel formation and the enclosure of water. Examples of those polymeric substances are starch in puddings, gelatin in desserts and in the water phase of fat spreads, pectin in jams, carrageenin in desserts and in the water phase of fat spreads, and many others.
In the second case entities such as air cells, water droplets, fat droplets, crystals, starch granules or casein micelles are dispersed into the food system. Interaction forces between such particles determine the consistency and the physical stability of the food products. Many food systems fall into this category. In yoghurt aggregated protein particles form a network of protein strands. In mayonnaise an "interconnected" structure of oil droplets is responsible for its consistency. In a shortening fat crystals form an interconnected network structure enclosing oil. In a margarine water droplets are dispersed into a continuous network structure of fat crystals and oil. So, this represents a dispersion of particles in a network of particles. Even more complicated structures are found in butter and ice cream. But in all those cases a build-up of structure from particles of particle networks can be distinguished, which is responsible for the consistency of the finished products.
Heertje et al. WO 92/09209 published Jun. 11, 1992 discloses finished foodstuffs containing mesomorphic phase of edible surfactants as a structuring agent or fat replacer. The formation of mesomorphic phases of edible surfactant molecules and water can give rise to a firm texture and consistency. The use of this property of mesomorphic phases, to give consistency to products, is new to the food business. However, it should be noted that this use may already be known in other areas such as cosmetics and pharmaceuticals.
This new way of product structuring may be described e.g. as a regular, molecular arrangement of surfactant molecules with intervening aqueous regions. For the purpose of the invention the term mesomorphic phase is intended to include all semi-ordered phases of water and edible surfactant materials. Examples of mesomorphic phases are cubic, hexagonal, alpha crystalline gel, beta-crystalline coagel and lamellar phases. Preferred mesomorphic phases for use in accordance with the invention are lyotropic phases; also preferred are lamellar phases. For the purpose of the present invention, the term lamellar phase refers to system having a pattern of alternating bilayers of edible surfactants and water. Examples of lamellar phases are lamellar droplet phases, lamellar gel phases and lamellar phases containing extended parallel layers of surfactants and water.
In the lamellar phase surfactants are believed to form a bilayer structure. It is believed that a bulk lamellar phase consists of stacks of bi-layer structures with an intervening aqueous phase. Products according to the present invention preferably comprise bulk regions of the lamellar phase whereas it has been suggested that known products of the prior art might contain boundary layers of this phase at interfaces, such as those found around oil-droplets in water-continuous fatty products.
The bulk lamellar phase may be formed by temperature cycling of a mixture of surfactant and water. In the crystalline state, the surfactant molecules are oriented with adjacent hydrophillic groups and the hydrophobic chains are parallel and densely packed. On contact with water and heating to the so-called `Krafft` temperature it is believed that water penetrates between the adjacent `head` groups to form a `liquid crystal` structure. On cooling below the `Krafft` temperature, the hydrophobic chains pack into a regular lattice, producing a one-dimensionally periodic `sandwich` structure of alternating surfactant and aqueous layers.
As an example of the `gel` structure obtained: for a mixture of water and a distilled monoglyceride made from fully hydrogenated lard, which has been cycled above the Krafft temperature, X-ray diffraction in the low-angle region reveals that the thickness of the monoglyceride layers is of the order of 50-60 Angstrom. As the proportion of water in the mixture in the system is increased the inter-planar spacing increases, as water is taken up between the monoglyceride layers. It will be realised that the fine structure of the mesomorphic phase, especially as regards the inter-planar spacing, will vary when different surfactants are used.
Another preferred mesomorphic phase according to the invention is a beta-crystalline coagel, which is believed to consist of small plate-like crystals having an average thickness of less than 1 fm or even less than 0.1 fm, said platelets being dispersed in an aqueous environment. This is a suspension of beta-crystalline emulsifier in water and is also known as a `hydrate`. These coagels may be formed instead of an alpha crystalline gel phase under certain conditions, such as at acid pH. Both the above mentioned alpha gels and these hydrates are used extensively in the baking industry as crumb softening agents in wheat bread and as cake volume improvers, but it is believed that the structure of the mesomorphic phase is lost during product preparation and consequently that the finished foodstuff (be it bread or cake) does not contain bulk mesomorphic phase. In the context of the invention the coagel phase is considered a semi-ordered phase of water and edible surfactant (mesomorphic phase).
The presence of mesomorphic phases in food products may be detected by any method suitable for the detection of regular arrangements of surfactant materials. Suitable methods include for example NMR, Electron microscopy, Differential scanning calorimetry, light microscopy and X-ray diffraction.
The use of mesomorphic phases of edible surfactants as structuring agent can lead to many useful applications, such as the use as fat replacer, foaming agent, egg white replacer, preservative, lubricating agent, consistency control agent, moisture retention agent and/or flavour release agent in foodstuff. A finished foodstuff may contain a mesomorphic phase of edible surfactant and less than 80% by weight of edible oil.
The present invention relates to the use of mesomorphic phases of edible surfactants as structuring agents in certain edible emulsions. It has been discovered that edible emulsions such as bread spreads, e.g., butter substitutes, containing mesomorphic phases can be improved by incorporation of certain sugars, particularly lactose. In a particularly advantageous embodiment, the addition of the sugar is combined with the removal of dairy ingredients other than lactose, which tend to buffer the composition. With this combination a better tasting, less acidic spread can be achieved.
Among spreads, the invention is of particular utility for spreads which are flavored so as to imitate butter (e.g., as opposed to say chocolate flavored spreads) since spreads suitable as butter substitutes generally do not include large amounts of sugar.
With respect to the use as fat replacer the present invention can provide edible compositions which have a reduced calorific contents as compared to normal foodstuffs. The present invention allows for the possibility of preparing foodstuffs with fat-like properties, but with the use according to the present invention containing essentially no fat at all or a very low amount of e.g. less than 5 wt. %.
In recent years there have been several developments regarding so-called "fat replacers." Such materials are intended to have as far as practical the functional and sensorial properties of fats, but to have a reduced calorie content and, where possible, health benefits as compared to fats. Much effort has been spent in the development of new materials which have a fatty functionality but are poorly adsorbed or non-digestible in the human gut.
Amongst such "fat replacer" materials are the sugar fatty acid esters, originally used as lubricants but now proposed for use in foods. The use of these sugar fatty acid esters as fat substitutes in margarines is suggested in EP-A-020 421 (Orphanos et al.: to the Procter & Gamble Company). Such margarines have a "fatty" phase which one or more triglyceride fats and one or more fat-replacers mixed intimately or in mutual solution. Food products are also envisaged which contain no triglyceride but have a "fat" phase consisting essentially of one or more fat replacers. Further reference to edible fat replacers can be found in U.S. Pat. Nos. 4,005,195 and 4,005,196 and EP-A-223856, 236288 and 235836.
Other glyceride related lubricants, especially the so-called hindered polyols having no hydrogen at the beta-carbon, such as the pentaerythritols and related compounds have been proposed as fat replacers (see e.g. U.S. Pat. No. 4,927,659 to Nabisco Brands Inc.)
Fat replacers comprising proteinaceous materials have been described. However, it should be understood that because these materials are digestible, they do not have as marked a calorie reducing effect as the above mentioned fat replacers.
Few of these materials, such as the sucrose esters or hindered polyols have completely understood physiological effects. It is generally believed that further experimental work will be required before the physiological effects are fully determined. There remains a clear need for fat replacers which comprise materials of well-understood physiological effect.
It has been found that the mesomorphic phase of edible surfactants can be used as a fat-replacing food component with a fat-like functionality and a simple composition. The invention provides products having a fatty oral impression, a plastic rheology and an improved taste.
Their use as foaming agent stems from the capability of the mesomorphic phase to stabilize air cells. It leads to very stable foam structure with air cells surrounded by a continuous structure of mesomorphic phase. This allows for its use in all products where air stabilization is essential, such as low fat substitutes for whipped creams, ice-cream and creaming margarines.
Their use as egg white replacer results from the excellent foaming capability mentioned above. This allows for its use in all products where raw egg white is used for foaming, such as bavarois type of products and toppings. This is very important in view of the danger of salmonella infection of raw egg white.
Their use as preservative is ascribed to the enhanced microbial stability, caused by the limited size of the intervening water areas in mesomorphic phase systems, which hinders the outgrowth of microorganisms. For example, the size(spacing) of the intervening water layers in a mesomorphic phase which is a lamellar phase system containing 95% water is approximately 0.1 fm, which is far below the size (1 fm approx.) of the effective microorganisms.
Their use as lubricant is connected with the fatty functionality and the proper rheology of these materials, even at a high water content. Two aspects are considered to be important in this respect: the hydrophobicity of the aliphatic chains of the applied surfactant molecules and the induced flow properties, e.g. in case of the mesomorphic lamellar phase structure the bilayers of surfactant molecules are separated by layers of water and are thus free to slide in relation to each other with the water as the gliding plane.
Their use as consistency control agent is directly connected with the structuring capability. The desired rheological properties can be achieved by proper choice of experimental parameters, such as concentration of nonionic and ionic surfactant, shear, pH and electrolyte. An example of such an application is in the design of spoonable and pourable products.
Their use as moisture retention agent is connected with the enclosure of the water between aggregated surfactant molecules. The physical state of water in foods influence the physical, chemical and functional characteristics of foods and food components, by influencing the water transport and/or the water mobility and/or the water activity. Their use in foodstuffs allows the introduction of large amounts of "immobilized" water, which can be freed at a later stage.
Their use as flavour release agent is connected with the possibility to entrap flavours in the water phase c.q. the surfactant phase of the mesomorphic phase. The nature of the systems would lead to a controlled release of the applied flavours. Many controlled release delivery systems have been described in the literature, e.g. the use of liposomes. Those systems have to be prepared separately and have to be added to the foodstuff as an extra and only in a limited amount. The use in foodstuffs allows the addition of flavour to the food system as such with proper retention of flavour components.
The mesomorphic phase and its method of preparation is known to food scientists. In the "Lipid Handbook" of Gunstone, Harwood and Padley (Chapman and Hall, 1986) such phases are mentioned at page 227. Further detail may be found in "Food emulsions" of S. Friberg (Marcel Decker, 1976 at page 82).
Such mesomorphic phases may advantageously be formed by heating a mixture containing the edible surfactant and water to a temperature above the Krafft temperature, followed by cooling.
It should be noted further that the above mentioned Lipid Handbook mentions at page 227 the use of mesomorphic phases of saturated, distilled monoglycerides as additives for processed potatoes or cake emulsions. However, this application is used for aerating bakery batters and enhanced complexing with amylose in non-finished starch based products. In the former application the aerating effect is ascribed to the better distribution of the monoglycerides in the batter system and in the latter application the monoglycerides form insoluble complexes with amylose, responsible for the crumb softening effect in bread and the texture improving effects on potato products and pasta foods. The emulsifiers are added to the bakery products before baking and to the potato products before final processing and consequently there is no mesomorphic phase in the finished products. The use of mesomorphic phases in such preparation methods for cake batters and processed potatoes are not embraced within the scope of the present invention.
In a preferred embodiment of the invention the mesomorphic phase is a lamellar gel phase. These phases are particularly preferred, because they can include a sensational amount of water, e.g. 98 or even 99 wt. %, based on the mesomorphic phase of edible surfactant and water.
Another preferred element of the present invention is the presence of bulk regions of mesomorphic phases in food products. Most preferred is the presence of bulk regions of mesomorphic lamellar phases. Bulk phases preferably consist of either a more or less continuous mesomorphic phase or of discrete particles of mesomorphic phase, for example having a number average particle size of between 1 fm and 1,000 fm. In this respect it should be noted that it has been suggested that known products of the prior art might contain non-bulk boundary layers of the lamellar phase at o/w interfaces, such as those found around oil droplets in water-continuous fatty products. The bulk regions of mesomorphic phase of edible surfactants may advantageously be used for replacing the aqueous phase and/or oil phase in food products in accordance to the invention.
Preferably food products in accordance with the invention contain at least 5% by volume of mesomorphic phase of edible surfactant, more preferred 10-100% by volume, for example 20-80% by volume, whereby the volume of the mesomorphic phase refers to the volume of the combined water/edible surfactant system.